After that A.M. gap-up -- to as high as $28.88 after a $28 even open -- FB closed down 3.4% at $27.04. Not a shock given the stock's recent strength; it's up roughly 55% over the last three months.

So, that's how a swing trader is handling Facebook, but what if you're a long-term investor.

First and foremost, there's nothing wrong with taking profits, even in a stock with legs. Never regret taking money off of the table. Doesn't matter if Facebook heads to $100 .

Did you get out with a capital gain? If you can answer yes, proceed to the next trade or investment. (For that matter, if you answer no, take your lumps and move along). As my colleague, TheStreet contributor Robert Weinstein likes to say: If you're not leaving money on the table, you're not making money . And, as I say, if a stock dumps you, don't come back to it, even for a quickie, on the rebound.

If you're not going to bank profits, accumulate.

The investing elite likes to scoff at the notion of dollar-cost averaging. They cite studies that show buying $10,000 worth of stock at one time works better than investing a little each month. Those studies are garbage, primarily because it's not possible to get a reliable sample. Plus, not everybody has ten grand to drop on one stock, let alone the handful or more they want to buy.

Timing matters too much in that mess. So don't waste your time with it.

Focus on your circumstances. How much money do you have to invest in a lump sum? How much can you invest weekly, bi-weekly or monthly? Do you have the time to mind your portfolio daily? Ultimately, you need to do what suits you. If you're not in the right stocks, it doesn't matter much when you buy them or how you spread out your investments, if at all.

Maybe lump-sum investing returns 8% on stock X in scenario Y, but only 6.8% via dollar-cost averaging. But, again, you waste time worrying about a percent here and there. It's the stock you select that matters.

An investment in Microsoft (MSFT) or Intel (INTC) five years ago didn't turn out quite as well as one in Apple (AAPL) or Amazon.com (AMZN) regardless of the method. It's easy to quantify the difference between 20% and 25% losses and 175% and 227% gains.